The present invention relates to a magnetically recorded/reproduced apparatus for a perpendicular magnetic recording.
Researches are being made into perpendicular magnetic recording as being adequate for a high-density magnetic recording system. A combination of a single-pole-type write head and a double-layered film medium comprised of a soft underlayer and a recording magnetic layer is often used in the perpendicular magnetic recording because of an intensive and steep recording magnetic field generated by a recording head. When magnetized information is reproduced by a reproducing head from a perpendicular magnetic recording medium subjected to magnetized recording, a reproduced signal from the head has a rectangular-shaped signal waveform corresponding to the magnetized recording pattern. A signal processing system adapted for data detection of the reproduced signal by perpendicular magnetic recording system is heretofore unknown well, but several techniques such as the partial response class I used in an optical recording/reproducing apparatus or the like, an extended partial response equalization system thereof (see JP-A-11-66755 laid-open on Mar. 9, 1999) and a technique similar to integral signal detection have been already proposed for an optical recording system or the like because the reproduced signal by perpendicular recording system contains a large amount of Dc signal component and is formed into a rectangular-shaped waveform.
Partial Response Equalization is a signal processing technique generally and widely used for an in-plane magnetic recording system. The Partial Response Equalization performs signal processing system in combination with a Maximum-Likelihood decoding system so that the signal-to-noise ratio of the reproduced signal can be improved and the data reproduction can be performed with high reliability.